The OWL devices are designed to monitor only one circuit, usually the incoming wires to the main electrical panel.

The OWL Intuition series (which may not yet be available in North America) allows users to view information via any Internet-connected computer or by using a smartphone via the OWL app.

Blue Line Innovations’ PowerCost Monitor

Blue Line Innovations’ PowerCost Monitor the sensing unit attaches to the outside of the electric meter.

Energy Inc.’s basic TED 5000, will monitor total household electricity consumption and show it on a small display.

TED uses one or more measuring transmitting units (MTUs) for each set of CTs, and up to four circuits can be monitored.

Wattvision monitoring has a pulse sensor installed at the electric meter.

Wattvision's monitoring sensor is connected via 50 feet of wire to a Wi-Fi gateway, which requires a 120 VAC receptacle.

Wattvision display on a smartphone

If you’re not comfortable with digging into your electrical panel to install a monitoring system, consider hiring a licensed electrician.

Intermediate

Measuring your home’s energy con­sumption is the first step toward finding ways to decrease it. While almost every residence has an electric meter, it usually only shows total household energy (kWh) consumed, although some include instantaneous power being used (kW). And the meter is usually placed where it is convenient for the utility—not for you—to read. But conservation-minded homeowners and renters can choose from several products that measure and record electricity consumption to reveal the energy hogs. The information is shown on a convenient countertop display or remotely on a smartphone or a computer screen.

If you want to use energy data to help reduce usage or convince other household members to adopt energy-saving behaviors, an energy monitoring system is for you. Or maybe you want to see how large a backup generator you need for utility outages, or how large a solar-electric system you need for your home. Maybe you just want to identify the biggest electricity loads in your household. If you already have a PV or wind system, you might need to monitor the on-site generation.

The Basics

A typical home energy monitoring system includes sensors, a data gateway, and a display to receive and view the information. Standard information includes energy consumption in kilowatt-hours (kWh) and power draw in kilowatts (kW). Often, monitors include the cost of the electricity consumed, and some allow programming with time-of-use rates.

Monitors require sensors at each point of measurement. Current transducers (CTs) and pulse sensors are most common. CTs are available in split-core or solid-core varieties. Split-core CTs make it easier to install in existing electrical installations, since you can open up the “donut,” and then close it around the wire. Note that CTs are typically not interchangeable between different systems.

A magnetic field is created as the current in the wire flows. When that magnetic field moves through the coil of the CT, it generates voltage proportional to the current flow. This voltage is measured by the electronics and converted into an amperage reading. At the same time, the voltage in the circuit is measured directly, and simple multiplication results in kW. Include the elapsed time, and kWh are computed. The other sensor type—pulse—counts the electronic pulses made by the utility meter as it counts units. Many utility meters for electricity, gas, and water are pulse meters. Simple pulse sensors are not sophisticated enough to determine whether the energy flow is incoming from consumption or outgoing from a home source, like a PV system.

Some meters gather more data from the sensors than others, updating readings every second compared to every 30 seconds. The way in which the data is used in calculating kWh or instantaneous kW will also influence the meter’s accuracy.

The sensors are hard-wired or communicate wirelessly through data loggers or transmitters that, in turn, send data to a local display. Some systems do not need or do not use a separate display. These transmitters are connected to the router so they can communicate within a local area network (LAN) and/or through third-party servers over the Internet. Several transmitters and gateways require a power supply and consume from 3 to 10 W. Most monitors allow information to be downloaded into a spreadsheet for further analysis.

We have a solution that listens to Cent-a-meter and OWL wireless meters every 60 seconds (and a growing list of solar grid-connect inverters) and charts it on the web. This is all using open-source software, so anyone can set up a system.

I did buy the EnviR. The transmitter comes with batteries but the display uses no batteries at all and runs only on the wall wart supplied. The HP article erroneously states that the display runs on batteries. The transmitter is made to install in a breaker box if outside and I would think it would diminish the signal strength. My breaker box is inside so I installed the transmitter on the wall bringing the CT leads through a knockout hole.

The transmitter sends out a data pulse every 10 seconds so if you have an appliance that cycles on/off the synchrony of the data pulse and on time of the appliance could be out of wack so that a long observation would be required to notice the on effect of the appliance.
John Nelson Nucla, CO

After reading the article, I was interested in "The Owl" monitoring system. Upon going to there website ( in the UK ) I find that the pictured Owl ( CM119) is not listed and replaced by the Owl micro
+. However, they list having in the package only one CT which to me would allow only monitoring of one phase of a 240 volt ( read half your circuits ), or monitor only one branch circuit. You need two CT's to monitor both hot 240v lines and get the full picture of the power going through your breaker box. HP article is misleading in saying the ".......incoming wires to the main electrical panel"

The description for the OWL products mentions that "The OWL devices are designed to monitor only one circuit..." If you're planning on monitoring more than one circuit, there are several good options covered in the article.

Hi John,
thanks for your comment. And yes this manufacturer is based out of the UK, however if you go to their website they list their USA distributor as Precision Data Systems: http://www.pdsmn.com/
Then if you go to their website and click on Products and Buy Now...you are lead to Amazon, who does offer the version with 2 CTs. Hope this helps!
Best,
Justine Sanchez
Home Power Magazine